DESCRIPTION: The research outlined in this application is designed to (1) characterize the transition to menopause in a well-defined cohort of U.S. women, (2) analyze patterns of individual-level variation in reproductive aging, (3) relate these patterns of variation to previous history including information on reproduction, menstrual patterns, and health, and (4) link the hormonal changes of menopause to the underlying etiologic process of follicular depletion. The study population includes women enrolled in the Tremin Trust project: these women have been providing detailed prospective reports of menstrual and reproductive histories and other information for up to 30 years. For around 150 of these women, urine specimens will be collected during a six-month window for up to five years.